The present invention relates to an introducer for deploying an implant within a body lumen, such as a curved lumen. It also relates to a method of deploying an implant within a curved lumen.
Stent grafts are used to replace or repair vessels of the body such as the arteries. A stent graft is usually formed from a tubular body of a biocompatible graft material with one or more stents mounted into or onto the tubular body to provide support therefor. The stents may be balloon expandable stents and/or self-expanding stents.
Endovascular methods have been proposed for treatment of an aneurysm of the aorta particularly where the aneurysm is adjacent the aorta bifurcation. However, when an aneurysm occurs higher up in the aorta, in the region of the descending aorta adjacent the thoracic arch or in the ascending aorta, endovascular techniques for treating these aneurysms are somewhat more difficult because of the tight curvature of the thoracic arch, the occurrence of major arteries in the region, and the proximity to the heart. Placement of a substantially cylindrical prosthesis in such a curved region can cause problems.
Stent grafts are typically deployed using endovascular techniques from an introducer device in which the stent graft is retained in a radially contracted condition by an outer sheath. Portions of the stent graft may be retained in the contracted condition by a release arrangement. Typically, the release arrangement includes a plurality of release wires, such as three release wires extending through a cannula, that can be attached to connecting members between the stent graft and the release wires. A plurality of release wires along the circumference of introducer device takes up a certain volume and limits the minimum achievable delivery profile of the introducer device. Further, loading and/or aligning each release wire with each connecting member makes manufacturing and assembly complicated. A single connecting member receiving a single release wire provides substantial stress along the release wire, causing deformation to the wire in the form a bends. Thus, the release wire is typically sized larger than necessary to withstand such stress and deformation. Moreover, the connecting members are typically free to slide along the release wire, thereby undesirably introducing stress to the cannula surrounding the release wires. Further, sliding connecting members can induce segments of the stent graft prematurely tilt or rock in undesirable and less predictable deployment configurations, which can increase the risk of unsuccessful implantation of the stent graft along the vessel wall.
Upon withdrawal of the sheath and release of any retention arrangement where provided, for example in cases in which the stent graft has self-expanding stents, the stent graft can expand under the action of the self-expanding stents towards the vessel wall to redefine the blood flow path. The introducer device is then withdrawn after deployment.
Currently, a stent graft is deployed in a curved lumen by causing the stent graft to follow the curvature imparted to the introducer device. However, this can result in the stent graft not sitting properly in the blood vessel and in the lumen of the prosthesis being closed off or reduced in diameter. Kinks can also occur along the length of the prosthesis and these can cause problems with restriction of flow in the lumen.
Furthermore, when deploying a stent graft that is substantially cylindrical in a curved aorta, there is a danger that the proximal end of the stent graft, i.e., the end nearest the heart, will not lie flat against the walls of the aorta. For example, the proximal end of the stent graft will not be positioned perpendicularly to the wall of the vessel. As a result, blood can flow underneath the edge of the proximal end of the stent graft, particularly on the inner side of the curve of the thoracic arch, and cause the stent graft to buckle and close off thereby causing serious problems.
In general, this application relates to the placement of prostheses in the aorta in the region known as the thoracic arch where the aorta leaves the heart and curves over in approximately a semi-circle to the descending aorta and then into the abdominal aorta and then into the lower limbs via the iliac arteries. The application is, however, not so restricted and can relate to placement of prostheses within or in place of lumens in any portion of a human or animal body, though it is particularly relevant to curved lumens, particularly tightly curved lumens. It would be desirable to minimize the overall delivery profile of the introducer device, to simplify loading of the release wire through the connecting members, and to provide a more predictable stent graft configuration prior to deployment and thus increase the risk for successful implantation of the stent graft.